58 UNITED STATES GEOLOGICAL SURVEY— TERTIAlll' FLORA. 



GYMNOGKAMMA, Desv. 



Oyin iiogra iiiiu a Gardncri, Lesqx. 

 Plate IV, Fig. 2. 

 Pieris Gardncri, Lesqx., Annual Report, 1873, p. 39.3. 



Frond l.irgo, simply pinnate; pinuas large, linear, broader in the middle, in right angle to tbo 

 racLis, rounded to tbe base; borders deeiily undulate ; middle nerve broad, grooved in the middle, flat- 

 tened on the borders; veins in an obtuse angle of divergence, abruptly curving downward at tbo base, 

 or decurring to the racbis, forking once or twice, joined by anastomoses and forming by cross-branches 

 irregular, long areola?. 



The large pinnse, three to three and a half centimeters broad in the 

 middle, where they are enlarged and broken, apparently lanceolate, with a 

 broad flat midrib, narrowly grooved in the middle, have entire but irregularly 

 undulate borders, and lateral veins at an open angle of divergence 70 to 80°, 

 thin, forking once near the base, sometimes twice, and here and there irreg- 

 ularly anastomosing by cross-veinlets. The substance is rather thin. I con- 

 sidered first this Fern as referable to Pteris^ as some species of this genus 

 have pinnjE of the same form, and the lateral veins sometimes anastomosing 

 as in Pteris grandifoUa Linn., which, however, shows this kind of division 

 of the veins only near the borders, and far more regular than in this species. 

 The genus Pteris has now two essential divisions: Heteroplilebium and 

 CamjJteria ; the first one has leaflets with lateral veins anastomosing toward 

 the margins, the second with veins connected at the base by arching vein- 

 lets. I supposed that the fragments described here might represent a section 

 intermediate between both, or with veins anastomosing in the middle of the 

 areas. But there is in Gymnogramma a species, G. Jajwnica, Desv., whose 

 characters are so evidently comparable to those of this fossil one that it seems 

 rational to admit it in the same genus. The Japan Fern has long, simple, 

 linear, oblong, acuminate pinnse, rounded at the base, the racbis flat on both 

 sides of the midrib, the veins close, forking once or twice, and joined by 

 cross-veinlets; all this as in the fossil species. The comparison of speci- 

 mens shows the relation to be very close. 



Count Saporta informs me that quite recently a Fern has been discov- 

 ered in the Gypses of Aix, representing a species winch he considers as iden- 

 tical with this, or at least closely allied. He is disposed to refer it to the 

 genus Chnjsodlum, a ."-cction of I lie Acrosiickimi. 



Habitat. — lioof ol' a coiil-niinc, Sand C!r('<'k, Colorado {A. (lardner). 



